1. Field of the Invention
The present invention relates to a touch panel and a display device, and more particularly to a technique which is effectively applicable in narrowing a width of a picture frame region outside an effective touch region.
2. Description of the Related Art
A display device which is provided with a device for inputting information with a touch operation using a finger of a user or a pen (contact pushing operation, hereinafter simply referred to as “touch”) on a display screen (hereinafter also referred to as a touch sensor or a touch panel) is used in a mobile electronic device such as a PDA or a portable terminal, various household appliances, an automated teller machine and the like.
As such a touch panel, a resistance-film type touch panel in which a change in a resistance value of a touched portion is detected, an electrostatic-capacitance type touch panel in which a change in capacitance is detected, an optical-sensor type touch panel in which a change in quantity of light is detected and the like are known.
The electrostatic-capacitance type touch panel has the following advantages compared with the resistance-film type touch panel and the optical-sensor type touch panel. For example, the electrostatic-capacitance type touch panel is advantageous with respect to a point that transmissivity is high, that is, approximately 90% thus preventing the lowering of quality of a display image compared to the resistance-film type touch panel and the optical-sensor type touch panel where transmissivity is low, that is, approximately 80%. Further, although the resistance-film type touch panel detects a touch position in response to a mechanical contact with a resistance film and hence, there exists a possibility that the resistance film is deteriorated or broken, there is no mechanical contact which brings an electrode for detection into contact with other electrode or the like in the electrostatic-capacitance type touch panel and hence, the electrostatic-capacitance type touch panel is advantageous also from a viewpoint of durability.
As the electrostatic-capacitance type touch panel, for example, there has been known a touch panel of this type disclosed in JP 2008-310550 A. In the touch panel of this type disclosed in the patent document, the touch panel is provided with electrodes arranged in the longitudinal direction for detection (hereinafter referred to as X electrodes) and electrodes arranged in the lateral direction for detection (hereinafter referred to as Y electrodes) which are arranged in a matrix array in two dimensional directions consisting of the longitudinal direction and the lateral direction, and an input processing part which detects a capacitance of each electrode. When a conductive body such as a finger is brought into contact with a surface of the touch panel, the capacitance of each electrode is increased and hence, the input processing part detects the increase of the capacitance, and calculates input coordinates based on a signal indicative of a change in capacitance detected by each electrode.
In the electrostatic-capacitance type touch panel disclosed in JP 2008-310550 A, lines are led out from one side of the Y electrodes (hereinafter these lines being referred to as lead lines), and the lead lines are connected to terminals which are connected to a flexible printed circuit board so that a drive voltage is supplied to the Y electrodes from one side of the Y electrodes. Hereinafter, the touch panel adopting such a method is referred to as a touch panel of one-sided feeding type.
In this touch panel of one-sided feeding type, to inspect a disconnection of the Y electrode or a disconnection of the lead line of the Y electrode, an inspection pad is arranged on the other side of the Y electrode.
Further, in this touch panel of one-sided feeding type, to make a width of a picture frame outside an effective touch region uniform on left and right sides and to minimize the width, it is desirable to lead out the lead lines alternately. However, to prevent an erroneous recognition of a touch position in the touch panel which is caused by capacitive coupling between a lead line arranged outside the effective touch region and the inspection pad, the lead lines are arranged in a region more outside the inspection pad.
Accordingly, the width of the picture frame is increased. On the other hand, the omission of the inspection pads for narrowing the picture frame gives rise to a drawback that the disconnection of the Y electrode or the lead line of the Y electrode cannot be inspected.